Galvano-scanners that can move a laser beam at high speed are used in laser machining and the like. Analog circuits suitable for high-speed processing are used in scanner drivers for galvano-scanners. Analog drive circuits can process data at high speeds, but can only perform simple control, and are unsuited to processes such as complex calculations and parameter conversions.
In view of the above, a method is proposed in Patent Document 1 in which complex computations for controlling the movement position of a galvano-scanner are performed in a digital computer, and the galvano-scanner movement position is controlled by an analog circuit using feedback on the basis of the calculated result. In Patent Document 2, a microcomputer for generating commands in which digital data for expressing scanner operation patterns have been written is mounted in a scanner driver, the digital data of operation patterns outputted from the microcomputer undergo analog conversion, and the scanner is driven and controlled via an analog drive control circuit. On the other hand, an electromagnetic limited-rotation motor having a detector that can be used as a galvano-scanner for mirror scanning is disclosed in Patent Document 3    Patent Document 1: JP-B 3513489    Patent Document 2: JP-A 2005-338450    Patent Document 3: JP-A 07-31119
In the case that a laser beam or the like produced by a galvano-scanner is moved to an arbitrary position in relation to a point of origin of a sensor, a command voltage that corresponds to the movement distance from the point of origin of the sensor to the movement destination can be applied. For example, in the case that a command voltage of 1 V is set to correspond to a command position of 1° from the point of origin of the sensor, and a command voltage of 10 V is set to correspond to a command position of 10° from the point of origin of the sensor, a 4-V command voltage can be applied when the laser beam is to be moved to a position of 4° from the point of origin of the sensor.
However, when one desires to move the movement position of a laser beam or the like produced by the galvano-scanner from the current position to an arbitrary position, it is necessary to apply as a positioning command a command voltage that is generated on the basis of the movement distance from the current position of the galvano-scanner. In other words, it is necessary to monitor a positioning signal outputted from the sensor that is mounted on the galvano-scanner, generate a positioning command voltage for moving the galvano-scanner to the movement destination position in which the movement distance has been added to the current position, and apply the command voltage to the galvano-scanner.
For example, in the case that the current position is a position 1° from the point of origin of the sensor, and one desires to move the laser beam position 3° from the current position, it is necessary to detect the current position 1° with the aid of the sensor, add a movement distance of 3° to the 1°, calculate 4° as the movement destination position, generate a command voltage of 4 V that corresponds to 4°, and continuously output the 4-V command.
Here, in the case that the laser beam or the like is to be moved from a current position on the workpiece to an arbitrary position, a host controller provided with a joystick or another operating member for inputting a movement distance in order to move to the new position is required.
However, drive control of a galvano-scanner is control in which constant tracking is carried out in relation to a positioning command. Therefore, in the case that a joystick or another operating member is operated to input a movement distance, real-time commands are involved, and there are therefore occasions when, for example, the galvano-scanner moves on an unintended movement trajectory even in a simple movement such as movement between two points. There are also cases in which it is difficult to stabilize the beam at the target position.